Ghost Strand Appears after Rendering?
Your problem is that you have Subsurf modifier before Hair, but forgot to enable Use modifier stack in Particle System. Moreover you hide Subsurf from viewport render, thus problem remains only in final render.

I assume you have to undo all Hair editing and enable Use modifier stack, then comb Hair from the start. Also your levels for Subsurf modifier are different for final render and viewport. This can cause another problems in the future.